The meat industry, including the poultry processing industry, faced challenges with cost effective handling of sludge that results from processing. Sludge originates as the watery waste from meat processing and from cleaning of the process facilities. By volume, sludge is primarily water, but sludge also contains waste such as bone chips, skin parts, animal by-products, and scraps, of which some is valuable animal fat, protein and other nutrients. Efforts are made to extract at least some of the water from the sludge, such as by drainage from holding tanks, for subsequent transfer of the at-least partially dewatered sludge to rendering plants. Dewatering reduces the volume of sludge that is to be transported by truck and thus lowers the cost of handling processing plant waste. Further, water supply systems require processing plants to filter and clean the waste water before return to sanitary sewer systems.
The rendering process dries the sludge and separates fats from valuable bone, protein and nutrients, which are referred to as Secondary Product Nutrients (SPN) that can be sold to mill manufacturers of livestock and aquaculture feed for further beneficial uses and products. However, free fatty acids develop quickly and build-up in the sludge. As the sludge deteriorates, free fatty acids build up, and as the free fatty acids increase, the valuable animal fat and protein nutrients decrease. High concentrations of free fatty acids prevent further processing and use of the valuable SPN. The SPN all too often wind up in landfills and essentially a profitable by-product for the meat processing industry is thrown away.
There are difficulties with sludge processing whether for return of water to sanitary sewer systems or for further use of SPN after rendering of the processing wastes. SPN within sludge is solid sensitive such that it is difficult to break apart properly and de-water. Belt press devices and gravity dewatering process have been developed but there are drawbacks. Primarily, the end result was typically a product that was a prime target for pathogens and free fatty acid growth. This defective product was waste and lacked value but also resulted in unpleasant plant odor. Often sludge was transferred to landfill without recovery of the lucrative animal by-products.
My earlier U.S. Pat. No. 8,163,176 discloses an apparatus and method for cracking the sludge to break apart the fat, protein and solids from the waste and water. The fat and solids float to the top surface of the water and problematic pathogens and bacteria evaporate. The water drains from the stratified sludge, and the resulting decanted solids contain the profitable SPN with animal fat, protein and other nutrients and beneficially, without significant water content, have a significantly reduced volume for transport. The water may be cleaned appropriately for return to sanitary sewer systems. The decanted solids have high quality SPN content, reduced free fatty acid growth, and decreased odor.
The disclosed apparatus for cracking sludge, while successful, nevertheless requires significant manual labor for operating the apparatus in the practice of the process, and further, for large commercially significant meat processing facilities there is a need in the art for continuous process under automation that incorporates the batch process feature for cracking an on-going supply of ferric and non-ferric watery sludge generated by such facilities. It is to such that the present invention is directed.